1. Field of the Invention
This invention generally relates to the field of data communication systems. More particularly, the invention presents an improved method for exchanging data rate information across a packet-based network.
2. Description of Related Art and General Background
With the unprecedented growth of the Internet, as well as the advances in computer technologies, the Public Switched Telephone Network (PSTN) has evolved into a main communication infrastructure for data traffic. Customer premise equipment (CPE) having communication capabilities, such as, for example, facsimile machines and modems, are now prevalent in both homes and offices. More often than not, CPEs rely on the PSTN infrastructure to provide connectivity to remote locations and support data traffic transport.
FIG. 1A depicts the conventional transport of data traffic across PSTN 108. As indicated in FIG. 1A, local CPE 102A and remote CPE 102B are respectively coupled by local access (i.e., local loop) to a telephone service provider's central switching office (CO) 104A, 104B. CPEs 102A, 102B are equipped with dial-up communication capabilities to initiate and establish connectivity. These capabilities operate in accordance with well-known communication protocols, such as, for example, ITU-T V series fax/data modem protocols, and in particular the V.34, Series V: Data Communication Over the Telephone Network, published in February 1998, the contents of which are herein expressly incorporated by reference. The V.34 protocol provides for the modulation, on-hook/off-hook, hand-shaking, and control signaling operations over PSTN 108.
Typically, a local CPE 102A initiates connectivity by dialing to remote CPE 102B, which accesses a switching mechanism in the local CO 104A. The local switching mechanism establishes an inter-office trunk connection to a remote switch in the remote CO 104B corresponding to the dialed remote CPE 102B. Upon achieving connectivity between the local CPE 102A and remote CPE 102B, a continuous, dedicated, circuit-switched, fixed channelized bandwidth is established for the duration of the call.
If the local and remote CPEs 102A, 102B are facsimile machines, the digital data scanned from the imaging portion is then modulated in an analog form suitable for transmission across the local loop wires and ultimately conveyed to the dialed facsimile machine. The transmission between the local CPE 102A and the remote CPE 102B operates in half-duplex mode. Similarly, if the local and remote CPEs 102A, 102B are modems, the digital data received from a connected computer is then modulated in an analog form suitable for transmission across the local loop wires and ultimately conveyed to the dialed modem. In such a case, the transmission between the local CPE 102A and the remote CPE 102B operates in full-duplex mode.
There are, however, drawbacks in the use of PSTN 108 to accommodate data traffic. For example, performance problems arise because data calls do not use the voice bandwidth efficiently. Data traffic tends to be bursty in nature and most of the time a data connection is not actually transmitting data it is simply reserving the connection in case it might use it. In addition, PSTN 108 was designed with the assumption that a relatively short call set-up time would be followed by a large amount of voice data being transferred. However, for data It transfers, the call set-up time in the PSTN 108 is very long relative to the length of the individual data transfers. This is exacerbated by the fact that, in order to minimize latency caused by call set-up times, most users leave their telephone connections off-hook for the entire time of the session, which may last several hours.
In an effort to alleviate some of these performance issues, telephone service providers 110 have developed Packet-Based Networks (PBN) on top of the PSTN 108 infrastructure to handle data traffic. FIG. 1B illustrates the conventional transport of data traffic across PBN 110.
As depicted in FIG. 1B, local CPE 102A and remote CPE 102B are respectively coupled by local access to local and remote COs 104A, 104B. In turn, local and remote COs 104A, 104B are coupled to local and remote gateway mechanisms (GWs) 106A, 106B, via PSTN 108A, 108B, respectively. Local and remote GWs 106A, 106B are configured to demodulate the analog data traffic received from the local and remote COs 104A, 104B into digital data and redirect the digital data to PBN 110.
Prior to conveying the digital data over the PBN 110, communication protocols, such as, for example, the aforementioned V.34 protocol, establish a local communications session between the local CPE 102A and local GW 106A and a remote communications session between the remote CPE 102B and remote GW 106B. In order to ensure proper operation and data transfer between the respective CPEs 102A, 102B and GWs 104A, 104B, these local and remote sessions include various handshaking, negotiation, and training procedures (e.g., V. 34 , Phase 2, Phase 3).
In particular, the V.34 protocol provides for the exchange of information sequences between the local CPE 102A and GW 106A and the remote CPE 102B and GW 106B during start-up, re-training, and re-negotiation sequences. These information sequences reflect the capabilities of, and the modulation parameters (e.g., MP, MPh sequences) supported by, the local and remote CPEs 102A, 102B and the local and remote GWs 104A, 104B. Embedded in the modulation parameter sequences, are the maximum data signaling rate supported by the local and remote CPEs 102A, 102B and the local and remote GWs 106A, 106B.
As such, prior to establishing the local and remote sessions, the maximum data signaling rates between the local CPE 102A and GW 106A and between the remote CPE 102B and GW 106B are exchanged and negotiated in order to determine the most suitable data signaling rates. There exists the possibility, however, that the most suitable data signaling rate between the local CPE 102A and GW 106A and the most suitable data signaling rate between the remote CPE 102B and GW 106B may be incompatible. At best, such incompatibility may result in sub-optimal data transmission performance. At worst, such incompatibility may result in the loss of data.